FIG. 5 is a sectional view showing a configuration of a conventional loudspeaker. In FIG. 5, a magnetic circuit having annular magnetic gap 24 is constructed by combining and bonding magnet 21, plate 22 and yoke 23. Frame 25 is coupled to this magnetic circuit. Voice coil 26 is movably fitted into magnetic gap 24 provided in the magnetic circuit. Diaphragm 27 is adhesively bonded to voice coil 26 at its inner peripheral portion, and to frame 25 at its periphery via roll-shaped first edge 28 that is adhesively bonded to the periphery of diaphragm 27. Suspension holder 29 is adhesively bonded to the middle portion between the inner periphery and outer periphery on the rear side (the side of the magnetic circuit) of diaphragm 27 at its inner peripheral portion, and to frame 25 at its periphery via roll-shaped second edge 30 that is adhesively bonded to the periphery of suspension holder 29. Dust cap 31 is adhesively bonded to the front surface side of diaphragm 27 so as to cover voice coil 26.
In the thus configured conventional loudspeaker, since first edge 28 and second edge 30 were symmetric and similar to each other, harmonic distortion of the speaker was reduced.
Note here that as information of prior art document relating to the invention of this application, for example, Japanese Patent Unexamined Publication No. 2004-7335 is known.
The above-mentioned conventional loudspeaker, however, had the following problems. That is, the conventional loudspeaker was manufactured by the following method. To frame 25 coupled to the magnetic circuit, second edge 30 adhesively bonded to the periphery of suspension holder 29 was attached with adhesive, followed by drying and curing thereof. Thereafter, adhesive was applied to adhesion portion 29a and diaphragm 27 was disposed thereon so as to couple the inner peripheral portion of suspension holder 29 to the rear surface of diaphragm 27. The adhesive applied to adhesion portion 29a of suspension holder 29 was a heating and drying type adhesive, which needed about 30 minutes of curing time. Therefore, productivity was bad. Furthermore, equipment for heating and drying is large, thus raising the cost of a loudspeaker.
Note here that since the change of such a heating and drying type adhesive to adhesive capable of being cured for a short time may be a factor affecting the property of a loudspeaker, adhesives cannot be changed easily.